Q.How many portable fire extinguishers are required on a maintenance truck with one
5 gallon diesel fuel can? How many are required on a diesel fuel transportation
unit?

A. All diesel-powered machines are required to have at least one 10A:60B:C portable fire
extinguisher (§§75.1907(b)(2) and 75.1909(a)(2)). Two portable fire extinguishers must
be installed when a 5 gallon diesel fuel safety can is carried on the vehicle (§75.1906(h)).
Diesel fuel transportation units must have at least two portable fire extinguishers
(§75.1906(h)). For diesel fuel transportation units that are towed (trailers), the towing
vehicle must have at least one portable fire extinguisher (two extinguishers if the towing
vehicle carries a safety can). Also, if the trailer portion of the diesel fuel transportation
unit does not have its own two portable fire extinguishers, two portable fire extinguishers
must be installed on the trailer before it can is disconnected from the towing vehicle.

Q.Section 75.1909(a)(3)(ii) requires the fuel tank to be protected from damage by
collision. The fuel tank on our pickup truck is located 10-12 inches above the
ground. Is this adequate to protect it from damage by collision with the floor?

A. This is a performance oriented standard. If the pickup travels on good road surfaces,
protection by location may be adequate. OEM's do not consider mine conditions for fuel
tanks on commercial vehicles. The operator should consider conditions in the mine
which may cause the potential of a ruptured fuel tank and fire and take appropriate
measures to prevent damage to the tank. This is not to be done on a trial and error basis.
A damaged fuel tank on a pickup truck constitutes a violation of Section 75.1909(a)(3)(ii)
and demonstrates the need to provide additional protection for similar vehicles operating
on the same roadways.

Q.Section 75.1909(a)(6) requires that all hydraulic tank fillers and vents be located to
prevent spillage or leaks from contacting hot surfaces. Does this include the engine
oil filler?

A. Yes. All hydraulic tanks, fillers, vents, and lines fall under the scope of §75.1909(a)(6).
Oil tanks, fillers, vents, and lines, including those for the engine, are covered by this
section. The requirement is based on fire accident data. Hot surfaces include the exhaust
manifold, piping, muffler, and exposed brake discs or drums. These surfaces can reach
temperatures which exceed the autoignition temperature for these fluids. Because this
regulation is performance oriented, an operator cannot rely on a trial and error approach.
If an operator believes that the location of the tanks and the methods used for filling
(including funnels, quick disconnect fittings, and extended filler tubes) will prevent
spillage, then as long as no spillage occurs the operator has complied with Section
75.1909(a)(6). However, if spillage onto hot surfaces does occur, then the operator must
adopt other methods.

Q.Section 75.1909(b)(5) requires lights on both ends of the vehicle. For pickup trucks
that have two headlights on the front, can one of these lights be removed?

A. No. For machines equipped with two headlights on the front by the original equipment
manufacturer (OEM), both headlights need to be maintained. Machines equipped with
only one headlight on the front and back of a machine by the OEM are acceptable.

Q. I have been advised that the service braking systems on some of my mining
equipment do not comply with the requirement that a single failure in the hydraulic
system not result in the loss of all braking capability. What means are available to
help me come into compliance with this requirement?

A. Section 75.1909(b)(6) requires "service brakes that act on each wheel of the vehicle and
that are designed such that failure of any single component, except the brake actuation
pedal or other similar actuation device, must not result in a complete loss of service
braking capability." Any service brake system design in which a single broken hydraulic
line results in the loss of all braking ability is prohibited. The system must provide the
same type of brake performance found in automobiles which have a dual piston master
cylinder that provides independent application of the front and rear wheels. However,
many existing diesel-powered mining vehicles use a single piston master cylinder or
pump to actuate all of the machine's brakes through a common hydraulic line. These
braking systems must be modified to comply with the rule.

Designs other than the dual piston master cylinder found on automobiles can be used. Machine manufacturers have developed retrofit kits, using specialized components,
which meet the requirements of the rule.

For existing machines, mine operators should contact equipment manufacturers for
assistance in meeting the requirements of §75.1909. Equipment manufacturers may offer
retrofit kits as well as engineering advice. Equipment manufacturers can provide
assistance in complying with safety requirements for their products. Rebuild shops may
modify the equipment or operators may make changes in-house. However, operators are
cautioned that some modifications to the brake system may impose significant
engineering difficulties.

Q.Do pins or bolts connecting service brake pedals and other service brake linkages require two means of preventing the pins or bolts from falling out?

A. Yes. Section 75.1909(b)(6) requires "service brakes that act on each wheel of the vehicle
and that are designed such that failure of any single component, except the brake
actuation pedal or other similar actuation device, must not result in a complete loss of
service braking capability." This requirement covers both the hydraulic components and
the mechanical linkages of the service brake system. The mechanical components that
are of concern are those components that secure pins and other linkages together.

Service brake systems frequently consist of a foot pedal mounted to a base plate. A brake
control valve is mounted on the opposite side of the base plate from the pedal. The brake
pedal connects to the base plate and to the brake valve usually through two or more
linkages. These linkages consist of pins or shafts and various types of retaining devices
that transmit force from the pedal to the brake valve. The pins or shafts by themselves do
not present any significant likelihood of failure. However, the retainers used to secure the
pins or shafts do have a reasonable likelihood of failure. These components are typically
nuts, cotter keys, or "E" clips.

Several aspects of these components need to be considered in deciding if they meet the
regulation. First, not all linkages are critical in the operation of the service brake system.
the rule covers only those connections that could fail and cause the loss of all service
braking capability. Second, there are many ways to provide two means to prevent a shaft
or pin from falling out. Welding an end cap on a pin would be considered acceptable so
would a nut with a cotter key. If using a nut and cotter key, the nut needs to be tight and
the design must positively prevent it or the shaft from rotating as the brake pedal moves.
The mine operator must ensure the cotter key is correctly sized for the hole in the shaft.
The cotter key should be corrosion resistant. Maintenance personnel should not reuse
cotter keys. A common lockwasher is not considered acceptable since it would fail when
the preload on the nut was lost. Two cotter keys to secure a shaft are acceptable under the
rule. However, when using two of the same device the possibility that both devices will
fail in the same manner and at the same time becomes more likely. In particular, we
consider the use of two "E" clips to be unacceptable since only a spring force holds them
in place and they can be pushed off at the same time. Finally, there are many possible
designs. The mine operator must evaluate each design to decide whether it provides the
performance required by the rule as requested. Also, since modifications to the brake
system may impose significant engineering difficulties, we recommend mine operators
rely on the equipment manufacturer for guidance in meeting this requirement.

We do recognize an exception to this requirement. Linkages in the braking systems of
commercial, on-highway pickup trucks that are typically used in underground coal mine
operations meet SAE and DOT requirements. We will accept these designs as meeting
the requirements of the regulation without modification. Maintenance personnel must
visually check the linkages of these vehicles during the weekly maintenance checks under
§75.1914(f).

Q.We have a six wheeled road grader, typically used in the construction industry, that
does not have brakes on the front wheels. Although §75.1909(b)(6) requires brakes
that act on each wheel, we consider there are other ways to provide the same safety
that would be provided by front wheel brakes. Will MSHA evaluate petitions for
modification of the requirement for front wheel brakes on graders?

A. Yes. MSHA will consider the grader's use and vehicle design characteristics including
the weight distribution and steering geometry when reviewing petitions for modification
to determine if the alternative method will provide the same degree of protection that
would be achieved by the installation of brakes on the front wheels. However, all other
§75.1909 braking requirements must be met. Depending on the equipment used and the
mining conditions encountered, at a minimum, alternate methods should include: 1)
limiting the maximum speed to less than 10 mph by physically blocking out gear ratios
that provide higher speeds, 2) providing training for grader operators to lower the
moldboard to provide additional stopping capability in emergency situations, 3) training
operators to recognize the appropriate speeds to use on different roadway conditions and
slopes, and any other terms or conditions necessary to provide the same degree of safety
as the standard.

Q.A heavy duty machine is equipped with a supplemental brake system. This system
has a separate brake release control as required by §75.1909(c)(4), however, this
control by itself does not supply release pressure to the brakes. To get pressure to
release the brakes the operator must push on the tram pedal. The circuit then
charges an accumulator that ensures the brake is fully released before fluid is
directed to the tram motors. Does the tram pedal constitute a second control to
release the brake that is prohibited by the rule?

A. No. Since the operator must release the brake with a single lever and expects the machine
to move when the tram pedal is activated, this arrangement complies with the rule. No
other machine control may release the brake. Note that without the accumulator in the
system the brakes could drag. This would not comply§75.1909(c)(6). The brakes must
be released before the machine is trammed and while it is being trammed.

Q.Some diesel-powered roof bolters have spring applied service brakes that
automatically apply when the tram lever is released. Do these brakes suffice as
supplemental brakes?

A. No. Diesel-powered roof bolters are defined as heavy duty equipment under the
regulations and as such must be provided with a supplemental brake system meeting the
requirements of §75.1909(c).

However, the service brake system on roof bolters typically consists of the same kind of
spring applied brake that is used as a supplemental brake on other types of equipment.
Common components between the service and supplemental brake systems are not
prohibited. Therefore, this type of service brake system may be modified to function as a
the supplemental brake system as well. This can be accomplished: 1.) with the addition
of a separate control that only applies and releases the supplemental brake, and 2.) the
addition of a hand pump to release the brakes while towing the vehicle. Both the service
and supplemental brake systems must be meet all the respective requirements for each
type described in the rule.

Q.If the supplemental brakes, required by §75.1909(c)(5), are manually released to tow
a vehicle do the brakes have to automatically reapply when the vehicle is started?

A. Yes. The supplemental brake system must be fully functional when the machine is
operating. If the supplemental brakes have been released manually, they must
automatically apply when the machine is restarted. If an operator fails to manually
release the pressure holding the supplemental brakes released, it would not be possible for
the brakes to apply within 5 seconds of engine shutdown as required by §75.1909(c)(1).
Further, if the manual release could override the brake system before the equipment is
started, operator error could cause precisely the types of accidents and injuries that the
final rule is intended to prevent.

Q.Is there a need to provide insulation over wiring studs, bolts, battery terminals, and
other connectors in starting circuits?

A. Yes. MSHA recognizes that on all diesel-powered equipment the charging and starting
circuits present significant risk of fire. Typically, starting and charging system
components are located in the engine compartment, where they are in close proximity to
potential fuel sources.Electrical faults in these circuits have been the source of serious
electrical fires. The regulations address this risk by requiring overcurrent protection, a
manual disconnect device, and the insulation of exposed, ungrounded connectors in the
starting and charging circuit. Further, all ungrounded connectors in other circuits located
in the engine compartment must be insulated to protect against the risk of fire caused by
the close proximity of the electrical circuits to potential fuel sources. Exposed connectors
can be insulated with electrical insulating coatings, sealers, covers or boots.

Q.Do the wiring studs, bolts, and other connectors in electrical circuits installed in on-highway vehicles, other than those in the starting and charging circuits and the
engine compartment, need to be provided with insulation? Are the wires sized and
fused adequately? Are the wires adequately protected from damage?

A. Commercial on-highway pickup trucks sold in the U.S. must comply with U.S.
Department of Transportation and Society of Automotive Engineers (SAE) standards for
electrical wiring systems. With some exceptions as described under the next question,
MSHA has determined that these systems comply with 30 CFR 75.1910 for use in
underground coal mines. The SAE standards require use of cables selected for a number
of factors, including: ambient operating temperature and temperature rise potential (both
during fault conditions and intermittent operation); the effects of exposure to fuels,
lubricants, and other chemicals and fluids to which the cable may be exposed;
mechanical strength; and, expected service life. The SAE standards also address cable
connections such as terminals and splices, as well as wiring harness construction, routing
and protection. Therefore, the electrical circuits and connectors are properly insulated,
sized, and fused, and they are adequately protected from damage except for the areas
described under the next question.

Q.What changes do I have to make on the electrical circuits on commercial pickup
trucks to meet the regulations?

A. Commercial pickup trucks may not comply with four provisions of §75.1910: 1) the fuse
required between the battery and starting motor, §75.1910(b); 2) the fuse required
between the battery and alternator, §75.1910(e); 3) the disconnect switch required as
close as practical to the battery, §75.1910(d); and 4) the insulation of all ungrounded
connectors located in the starting and charging systems and in the engine compartment,
§75.1910(f). If ungrounded connections in the engine compartment are completely
enclosed in a box that holds only electrical components, insulation is not required.
Finally, no modification is required for the OEM connectors located outside of the engine
compartment.

Q.What electrical protection is required for alternators?

A. The alternator must be protected by an overcurrent device to comply with Section
75.1910(e). First, for commercial pickup trucks, the wire installed by the vehicle
manufacturer is considered adequate for compliance. However, a fuse or other
overcurrent device must be installed in the wire. The fuse can either be rated for the
output of the OEM alternator, or be the next higher size fuse if no fuse is manufactured
exactly at the alternator output rating, or the fuse size specified by the pickup truck
manufacturer. Second, for all other heavy duty, light duty, and portable equipment the
wire size and fuse rating must conform to the National Electric Code (NEC), 1968. NEC
specifies that the wire must be protected at no greater than 125% of its rating and the
Code also permits the next higher size fuse when the exact fuse rating is not
manufactured. In either case, if the alternator manufacturer provides written
documentation based on the duty cycle of the alternator, that wire and/or fuse sizes
different than that specified by NEC are appropriate, then the alternator manufacturer
recommendations are acceptable for compliance.

Q.We are taking the bed off a pickup truck and installing a compartment to transport
personnel. We are adding our own wiring and lights for this compartment. What
regulations do these lighting circuits have to meet?

A. Any mine operator installed wiring on commercial pickup trucks must meet all the
requirements of §75.1910. For overcurrent and short circuit protection and wiring size, in
particular, §§75.1910(a) and (f) reference §75.513-1 and §75.518-1. These sections
reference the National Electric Code, 1968, specifications for circuit protection and wire
size.

Q.Is there a need to provide insulation over wiring studs, bolts, battery terminals, and
other connectors in branch circuits, in addition to the starting circuit, on diesel-powered equipment other than commercial pickup trucks?

A. Yes. Section 75.1910(f) is intended to prevent ungrounded connectors from arcing. This
can be accomplished by insulating the connectors with electrical insulating coatings,
sealers, covers or boots or by completely enclosing the electrical connections in a box
containing only electrical components.

Q.We have looked at fuses for protecting the starting circuit and have found fuses
other than the those listed by MSHA on its homepage, to provide adequate
protection. Specifically, we have installed a Littelfuse, Inc. Megafuse 225 on an
Isuzu pickup truck with a QD 60 engine. Is this acceptable?

A. Yes. The MSHA fuse listings provide a source for acceptable fuses for specific engines,
starters, system voltage, and types of wire and insulation. Other fuses can provide
equivalent or better protection. By better protection, MSHA means the fuse will
interrupt the circuit sooner under a given load. Although the Megafuse 225 provides
better protection by opening sooner than the fuse MSHA lists, it is more likely to
interrupt the circuit during the winter months when the engine is harder to crank. The
next larger size Megafuse, the 250, provides less protection than the fuse MSHA lists and
does not comply with §75.1910 for starting circuit protection.

Q.Can the OEM battery cables in commercial pickup trucks be used with the fuses
listed on the MSHA homepage for engines in these vehicles?

A. Yes. The OEM battery cables in commercial on-highway pickup trucks sold in the U.S.
meet SAE specifications. These specifications include tests of the cables after they are
conditioned to at least 110°C. The fuses listed on MSHA's homepage are sized for
battery cables rated at 90°C. Since the OEM battery cables are tested after being
conditioned to a higher temperature they are considered acceptable for use with the fuses
listed by MSHA.

Q.Section 75.1910(d) requires a circuit-interrupting device that can deenergize all
power conductors. Does a removable fuse or plug installed in the wire from the
battery meet the requirement for a disconnect switch?

A. No. Fuses, plugs, and similar devices may not be recognized as a switch in an emergency
situation. In addition, fuses and plugs have tight fits to be electrically efficient making
them difficult to disconnect. Also, the fuse or plug assembly must be grasped tightly by
the user to make or break connections. In an emergency situation, the assembly and
associated wiring may become extremely hot and the user may suffer contact burns to the
hands while disconnecting the cable. Further if the circuit is disconnected under load, an
electrical flash could result that may injure personnel.

To comply with Section 75.1910(d) the switch must be a manual switch. A push button
or rotatory switch, a manual reset circuit breaker, or contactor relay may suffice in this
application provided: 1) it is placed in each ungrounded (power) conductor; 2) located as
close as practicable to the battery terminals; 3) properly selected and installed in a circuit,
in order that it may be operated within its electrical ratings safely and without damage
underfull load; 4) not automatically reset after being actuated; and 5) be designed or
otherwise mounted in a manner which precludes its closing by force of gravity. The
switch should be placed between the battery and fuse to allow the fuse to be changed with
the power off. The switch must be designed to safely open the circuit under load in
emergency situations. MSHA has evaluated several switches for different circuits and
will list acceptable switches on the MSHA diesel information web page. To determine
the acceptability of other switches, please contact Arlie Massey or Bob Boring at the
Approval and Certification Center, 304-547-0400.

Q.If a mantrip is only required to have a manual fire suppression system installed by
§75.1909 but an automatic fire suppression system is required by §75.380(f)(5)(i),
does the fire suppression system need to only meet the requirements for fire
suppression systems under §75.380 or does it have to meet all the requirements
under §75.1911? Also, the system currently used is not a stand alone system that
would meet the requirements of 75.1911(f). Wouldn't removal of the automatic
portion of the fire suppression system to comply with 75.1911(f) be a decrease in
safety by not providing automatic detection of fires?

A. If an automatic fire suppression system is installed on a diesel-powered machine, it must
meet all §75.1911 requirements. The requirements in §75.1911 define a well engineered
system specifically for diesel-powered equipment. Systems that do not meet §75.1911
requirements are not as well engineered and may not provide operators with the degree of
fire suppression system effectiveness they expect. This could compromise safety.
Further, automatic fire suppression systems that meet all of the requirements of §75.1911
are readily available.

Q.If an outby electric roof bolter is converted to diesel power, do the panic bars have
to be maintained on the vehicle?

A. Yes. If an outby electric roof bolter is converted to diesel power and the machine was
equipped with a panic bar from the original equipment manufacturer, the panic bar is
considered to have been supplied as a safety device and, therefore, must be maintained
under §75.1914(a).

Q.What types of devices are considered safety devices under §75.1914(a)?

A. Components that reduce the risk of injury to workers or reduce the risk of fire or
explosion are considered safety devices. Devices that only protect machinery from
damage are not safety devices. For example, a governor that prevents an over speed
condition that, if it occurred, would result in failure of nonessential machine component
or voiding of a warranty would not be considered a safety device. However, if the failure
of the governor permitted an over speed condition that could cause the machine to break
apart and possibly injure nearby personnel, it would be considered a safety device.
Similarly, with over temperature devices, if exceeding the temperature limit would only
cause machine damage and not increase the risk of fire or otherwise endanger personnel it
would not be considered a safety device.